/*
 * C.cpp
 *
 *  Created on: 2012-5-30
 *      Author: ncrd
 */


#include <cstdio>

int main (void) {
	int n = 12;
	float sum = 0;
	while (n--) {
		float i;
		scanf("%f", &i);
		sum += i;
	}
	printf("$%.2f\n", (float)sum/12.0);
}
